1. Field of the Invention
The present invention relates to a cable release for winch operated drop curtains which allows the curtains to drop without unwinding cable from the winch as is needed in all other curtain control systems.
2. Brief Description of the Prior Art
Commercial livestock confinement buildings for poultry or hogs are artificially ventilated and include openings in the sidewalls which are closed with drop curtains. Forced ventilation allows for growing more animals at less expense in less space. During normal operations, the electric ventilating fans constantly remove carbon dioxide and heat generated by the animals and continuously provide fresh air. The curtains may be partially opened and closed as necessary to maintain the proper temperature for the animals.
In the event of a power failure in the electric ventilation fans or an unusual increase in the inside temperature, it is necessary to take immediate action as overheated, densely packed animals can suffocate and die. Such action usually consists of opening all of the curtains allowing cross ventilation for the animals through the sidewall openings.
Typically in such confinement buildings, the curtains are raised and lowered with a cable which is operated by a winch. A curtain drop device responsive to power failure or increase in temperature is attached to the winch handle, which when freed allows the cable to unwind from the winch and the curtains to drop. There are a number of different curtain drop devices as discussed below which rely on the winch as the safety device. There are problems, however, with these systems. For example, if the winch mechanism is rusty, the release action may fail and the animals may die. Rusting is not an uncommon occurrence as the atmosphere in a livestock confinement building is very corrosive. Even if the cable, winch gears and winch bearings are not corroded, as the cable is wound on the winch under the weight of the curtains, wraps of the cable may lodge together such that the cable does not unwind properly when the handle is released. Other problems arise, for example, if an operator fails to release a locking dog on the winch after raising the curtains and attaching the curtain drop device. Further, when the curtain drop device includes a cord release, sometimes the cord entangles in the winch stopping the cable from properly unwinding and the curtains from dropping. In view of these problems, there is a need for a cable release which does not rely on the winch as the safety device.